/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.queryengine.plan.relational.planner.iterative.rule;

import org.apache.iotdb.db.queryengine.plan.relational.planner.Symbol;
import org.apache.iotdb.db.queryengine.plan.relational.planner.iterative.Rule;
import org.apache.iotdb.db.queryengine.plan.relational.planner.node.CorrelatedJoinNode;
import org.apache.iotdb.db.queryengine.plan.relational.utils.matching.Captures;
import org.apache.iotdb.db.queryengine.plan.relational.utils.matching.Pattern;

import java.util.List;
import java.util.Set;

import static com.google.common.collect.ImmutableList.toImmutableList;
import static org.apache.iotdb.db.queryengine.plan.relational.planner.SymbolsExtractor.extractUnique;
import static org.apache.iotdb.db.queryengine.plan.relational.planner.node.Patterns.correlatedJoin;

public class PruneCorrelatedJoinCorrelation implements Rule<CorrelatedJoinNode> {
  private static final Pattern<CorrelatedJoinNode> PATTERN = correlatedJoin();

  @Override
  public Pattern<CorrelatedJoinNode> getPattern() {
    return PATTERN;
  }

  @Override
  public Result apply(CorrelatedJoinNode correlatedJoinNode, Captures captures, Context context) {
    Set<Symbol> subquerySymbols =
        extractUnique(correlatedJoinNode.getSubquery(), context.getLookup());
    List<Symbol> newCorrelation =
        correlatedJoinNode.getCorrelation().stream()
            .filter(subquerySymbols::contains)
            .collect(toImmutableList());

    if (newCorrelation.size() < correlatedJoinNode.getCorrelation().size()) {
      return Result.ofPlanNode(
          new CorrelatedJoinNode(
              correlatedJoinNode.getPlanNodeId(),
              correlatedJoinNode.getInput(),
              correlatedJoinNode.getSubquery(),
              newCorrelation,
              correlatedJoinNode.getJoinType(),
              correlatedJoinNode.getFilter(),
              correlatedJoinNode.getOriginSubquery()));
    }

    return Result.empty();
  }
}
